1. Field of the Invention
This invention relates to an electrically insulating coating glass, and more particularly, it relates to an electrically insulating coating glass for fusing or coating an electroconductive material, especially a paste of an electroconductive powder, e.g., silver paste, which is used for the cross-over insulation required for multi-layer circuits, e.g., hybrid I.C.
2. Description of the Prior Art
An electrically insulating coating glass powder has been used for sealing, fusing or coating preformed products made of glass, ceramic and metal in addition to semiconductor elements, semiconductor parts or the like.
Integrated circuits, and displays are formed by screenprinting an electrically conductive layer, a resistance layer and an electrically insulating layer onto a substrate made of alumina or other non-conductor. To be suitable for use in an I.C., the electrically insulating layer should be easily screen-printable, have high insulation, low dielectric constant and low dielectric loss, should cause no flow of the printed pattern upon firing at a suitable firing temperature, should be inert to pastes of electroconductive powder and resistive powder, should impart no harmful affects to solder or soldered lead, should have a high density and high degree of flatness after printing and firing, should be highly adhesive to the substrate, and should possess high resistance to humidity.
Heretofore, the insulating layers have been made of crystalline glass of the SiO.sub.2 --Al.sub.2 O.sub.3 --PbO--TiO.sub.2 --BaO type, as disclosed in U.S. Pat. No. 3,586,522, or the SiO.sub.2 --Al.sub.2 O.sub.3 --PbO--ZnO--B.sub.2 O.sub.3 type.
However, these conventional electrically insulating crystalline glasses are difficult to melt. They impart disadvantageous electrical characteristics, cause the printed pattern to flow easily because the glasses are of the surface devitrifiable type, and they have a low chemical durability.
A need exists therefore for an electrically insulating glass which will form an insulating layer with the desirable characteristics stated above.